1. Field of the Invention
The invention relates to holding devices and in particular to an apparatus for holding a tool, such as a doctor blade, utilized to regulate the coating thickness in the coating of a web of material.
2. Description of Related Technology
A doctor blade holding apparatus disclosed in DE 20 08 082 (corresponding to Nolden, U.S. Pat. No. 3,683,851 (Aug. 15, 1972)) includes a clamping mechanism for holding a mounting plate, a doctor blade support attached to the mounting plate and a doctor blade or rod (identified as a round rod scraper in U.S. Pat. No. 3,683,851) mounted on the doctor blade support. A pressing tube exerts pressure on the doctor blade support which in turn presses the doctor rod onto a web of material wrapped onto a counter roll of a coating machine. The mounting plate of such a device is typically in the form of a leaf spring.
Process requirements may compel the replacement of the doctor blade support and the doctor rod with a coating blade, which is also typically in the form of a leaf spring. It would be desirable to replace a doctor rod with a coating blade without extensive rebuilding of the apparatus. However, this is made very difficult in some embodiments of the known device according to DE 20 08 082 where the doctor blade support is vulcanized onto the mounting plate.
However, it has become a customary practice to use doctor blade supports which have a holding strip attached to them. The holding strip secures the doctor blade support to the mounting plate. As a result, the doctor blade support can be replaced easily without having to discard the mounting plate. However, even in such embodiments, it is almost impossible to replace the doctor blade support, together with the doctor rod and the mounting plate by a coating blade without significant rebuilding of the apparatus.